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on switch of a technics amp

eastwestboy

New Member
Hello, I have a 20 year old technics amplifier SA-R230L, it’s in very good shape, but most times when I switch it on I hear the relay click, the standby lamps goes off, the lights on the equalizer go on, but it is not turning on. All other lights stay off and the unit stays off. Sometimes after about 15 minutes it switches on all by itself. Anybody with an idea? Thanks from eastwest.
 

btcg

New Member
The relay is most likely bad, and/or has dirty (gutted) contacts.

If you can get the plastic top of the relay off, you can take a burnishing tool and lightly clean the (WITH THE UNIT UNPLUGGED) contacts. The missus metal finger nail file or thin Emory board will work too.

Replacing it should be cheap.
 
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eastwestboy

New Member
Thanks for the answer. I checked again, it has 2 relays. One is for the power supply, this one is ok. The other is on the cicuit board and is time delayed. It activates 3 seconds after power on and is the for the speakers. It also works, 2 contacts close if there is voltage on the coil, and there is continuity between the contacts The thing is: When the failure happens, this relay does not activate. The problem is sometimes there is voltage and sometimes no voltage on the coil. When there is no voltage the whole front panal is dark except the tips on the equalizer movers and the unit is not working. A schematic would be very helpful. Anybody has a good guess?
Thanks from eastwest
 

btcg

New Member
Check your connections, and if you have an ESR meter, check the electrolytics.

Old filter capacitors in the power supply (and yours are 20 yrs old) may not be be up to snuff.
 

eastwestboy

New Member
Thanks,
I am contemplating the next steps. Since it is a big pain to remove the circuit board, I have to know in advance what I am gonna do. Because it is not a reproducible failure, it sometimes doesn’t happen for quite a while, the el.caps would pobably test ok. So what about just replace all el.caps in the power supply, those are all on the main board. What are my odds? There are 2 6800uF caps and about 10 small ones. Something that puzzles me: if I wiggle the speaker relay a bit with my finger (with plasic cap on), the amp comes back to life. This relay however always works and is only for the speaker contacts. All connections seem to be ok, good quality of manufacture inside.
Thanks from eastwest
 

btcg

New Member
Because it is not a reproducible failure, it sometimes doesn’t happen for quite a while, the el.caps would pobably test ok.

Actually, they wouldn't (and I'm taliking about the smaller ones). I'd wager you'd have a small handfull that would have higher than normal ESR levels. I have a Creative Electronics ESR meter, and in old units like yours you can easily identify caps that are even partially dry. It is, after all, a 20 year old unit. More on this later.

2-6800mfd-WOW...that is an old unit.

You wiggle the relay and it comes on? The contacts are probably gutted.

Assuming you've checked your connection, and resoldered any cold solder joints, here's what I'd do:

replace the relay.

If that fixes it, and you don't have an ESR meter and care about about long term operation, you're all set.

If you're looking long term:

Take a shotgun (an old-time Tech term) approach:

You've only got about 10 small electrolytics? Replace them all. It's cheap enough.
 
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